Various methods for the preservation of biological specimens have evolved over the years. Modem specimen preparation techniques for microbiology and electron microscopy typically include dehydration and immobilization, both of which are irreversible and often damage the integrity of the specimen.
Dehydration using chemicals or freezing temperatures typically causes structural damage to biological tissues. Chemicals may destroy the overall quality of the specimen, including the particular characteristics of interest to the scientist. Rapid freeze-drying often produces crystalline structures that are destructive to most biological tissues. The result of dehydration is a biological sample that has been significantly altered, beyond repair, from its natural state.
Immobilization of a biological sample within a polymer typically involves curing, using elevated temperatures or ultraviolet radiation, both of which are detrimental to specimen quality. The polymers and resins typically used for sample preparation today form a hard plastic when cured. Once a sample has been cured, the biological material cannot be restored to its isolated state.
Biological specimen preservation techniques are of particular concern in the preparation of biosensors. Biosensors are used in the health and environmental sciences for rapid detection of specific substances. Biosensors are currently used to detect the presence of pesticides, herbicides, and other compounds; to detect the presence of organic compounds such as alcohols, ammonia, and metals; and, to detect the presence of specific bacteria including algae, fungi, and pathogenic organisms such as Escherichia coli (E. coli) and Salmonella. Potential applications for biosensors include sensing pollution and microbial contamination of air and water, clinical diagnosis of medical conditions, fermentation analysis and control, monitoring and analysis of industrial gases and liquids, monitoring of mining conditions and sensing toxic gases.
Biosensors often have a very short shelf life because the antibody or other biological receptor degrades rapidly when exposed to the environment. Like other biological samples, biological receptors need isolation and protection from the environment until ready for use. In field applications, especially, a variety of biological receptors may be needed at any time, depending upon the conditions.
There is an unsatisfied need in the art for biological samples that can be protected and preserved without altering or destroying the biological tissue. The demand for safe transport and prolonged storage of biological samples today requires preservation techniques that maintain the integrity and quality of the biological sample. Sensitive biological receptors used in biosensors need to be isolated from the environment, without damaging the receptor, until ready for use. None of the specimen preparation techniques in the art currently meet these needs.
There is also a need in the art for biological samples that can be restored to their isolated or prepared state after immobilization, with minimal damage, for later study or use. The current techniques of dehydration and immobilization are irreversible and destroy sample viability. Restoration is particularly critical for the biological receptors in biosensors, which are especially sensitive. There is a need, therefore, for a preservation technique that is both harmless and reversible.